The subject matter disclosed herein relates generally to imaging systems capable of operation in multiple modalities, and more particularly to an apparatus and method for aligning a multi-modality imaging system.
Multi-modality (also referred to herein as multi-modal) imaging systems are capable of scanning using different modalities, such as, for example, but not limited to, Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI). The difference between multi-mode and multi-modality is that in multi-mode systems the same hardware is utilized to perform scans in different modes (e.g., a radiation source and a radiation detector is used in both a flouro mode and a tomosynthesis mode). In a multi-modal system, although some of the same hardware is utilized to perform different scans (e.g., an image produced by PET is processed and displayed respectively, by the same computer and display, as an image produced by MRI), the data acquisition systems (also referred to a modality units) are different. For example, on a PET/MRI system, a radiopharmaceutical is typically employed in tandem with a PET camera to acquire PET data and a radio frequency (RF) coil is used to acquire MRI data.
In multi-modality systems, for example, an integrated PET/MRI system, the PET data and MRI data should be inherently registered with one another. Since the patient lies still on the same table during the PET and MRI portions of the acquisition, the patient should be in a consistent position and orientation during the two acquisitions, greatly simplifying the process of correlating and fusing the PET and MRI images. Inherent registration of the PET images and MRI images assumes a known alignment of the PET and MRI coordinate systems, consisting of at least a known spatial transformation between the two coordinate systems. Misalignment of the coordinate systems can result in a mis-registration of the images between the two imaging modes.